A functional developer roller for use in contact electrophotographic printing having a high resistance surface layer over a semi-conductive core gives excellent print performance independent of the speed of movement of the printing members (termed process speed). This is an improvement over a more common method which involves making a semi-conductive core and subsequently coating that core with a resistive material in a separate process such as spray or dip coating.
By using the novel combination of materials described in the foregoing U.S. Pat. No. 5,707,743; a high resistance surface layer over a more conductive core can be produced simply by oxidizing the roll surface. This eliminates the need for coating the conductive roll with a resistive layer in a separate process. This process is an improvement over a more common method which involves making a semi-conductive core and then subsequently coating the core with a resistive material in a separate process such as spray or dip coating. Oxidizing can be more cost effective than spray or dip coating and produces a roller with less defects. The oxidized polydiene-based roll of this invention mimics the electrical performance of the coated roller and gives excellent print performance over a wide range of process speeds.